孔道压浆缺陷对预应力混凝土梁力学性能的影响

Analysis on Mechanical Properties of Prestressed Concrete Beams with Grouting Defects

预应力孔道压浆在预应力体系中起着保护预应力筋免遭锈蚀、将预应力筋和孔道壁粘结起来与周围混凝土结成整体、保证预应力在梁体内的有效传递等作用。预应力孔道压浆质量直接影响着预应力筋能否充分发挥作用。本文首先进行了预应力孔道压浆缺陷对预应力混凝土梁力学性能影响的试验,建立了试验梁数值分析模型,并与试验结果进行了对比分析,分析了压浆缺陷大小和位置分布对预应力梁抗弯承载力的影响;然后扩展数值模型分析了预应力孔道压浆缺陷对足尺预应力混凝土箱梁力学性能的影响。结果表明:随着孔道压浆缺陷长度的增加,箱梁的极限抗弯承载力逐渐减弱,但消弱程度较小,当压浆缺陷长度占箱梁总长15%时,对其承载力的削弱仅为4%;对于等长度的压浆缺陷,集中对称分布于跨中的缺陷对箱梁极限抗弯承载力的削弱作用小于对称分布于梁两端的缺陷;对称分布于梁两端的缺陷对箱梁极限抗弯承载力的削弱作用小于集中分布于箱梁一端的压浆缺陷。

Prestressed channel grouting plays a role in protecting the prestressing tendons from corrosion in the prestressed system,bonding the prestressing tendons and the channel walls together with the surrounding concrete,and ensuring the prestress effective transfer in the beam.The prestressed tunnel grouting quality directly affects whether the prestressed tendon can fully function.The influence of the prestressed channel grouting defects on the prestressed concrete beams mechanical properties was firstly tested.The test beams numerical analysis model was established and compared with the test results.The grouting defects size and position distribution were analyzed.Then,the established numerical analysis model was extended to analyze the influence of prestressed channel grouting defects on the full-scale prestressed concrete box girder mechanical properties.The results show that the box girder ultimate flexural capacity decreased with the grouting defect length increasing,but the weakening degree was low.When the grouting defect accounted for 15%box girder length,the bearing capacity was weakened to 4%;For equal-length grouting defects,the weakening effect of concentrated and symmetrically distributed mid-span defects on the box girder ultimate flexural capacity was less than that of symmetrically distributed ends at the beam.;The influence of the defects symmetrically distributed at the ends of the beam on weakening the box girder ultimate bending capacity is less than the grouting defects concentrated at one box girder end.